Evaluation of right ventricular performance in patients with postoperative congenital heart disease using Doppler tissue imaging and cardiopulmonary bypass indices: A prospective cohort study

Abstract Background and Aims Postoperative cardiac outcomes after intracardiac repair (ICR) are determined by numerous factors whereas right ventricle (RV) dysfunction is considered essential for them, as only few studies attempted to evaluate it postsurgically. RV's function is supposed to be the strong prognostic factor for patients diagnosed with congenital heart defects; therefore, assessing it is the main objective of the study. Methods This is a prospective single‐centered cohort study performed on 50 pediatric patients with congenital heart disease (CHD) who underwent ICR between January 2019 and January 2022. All patients underwent echocardiographic assessment of RV function via tricuspid annular plane systolic excursion (TAPSE) and fractional area change (FAC) at 1, 24, and 48 h. After surgery, where pre‐ and postoperative RV pressure, cardiopulmonary bypass (CPB), and aortic cross‐clamp (ACC) time were assessed. Similarly ventilation intensive care unit (ICU) and hospital stay times and mediastinal drainage were also monitored. Results The mean ± standard deviation for pre‐ and postoperative RV pressure was 49.1 ± 16.12 and 42.7 ± 2.9 mmHg, respectively, whereas that for pre‐ and postoperative pulmonary artery pressure was 30.4 ± 2.6 and 24.2 ± 12.9 mmHg, with p value of <0.002 and <0.001, respectively. The mean ± standard deviation of CPB and ACC times was 120.92 ± 74.17 and 78.44 ± 50.5 min accordingly, while those for mean ± standard deviation of ventilation time, mediastinum chest drainage, ICU and hospital stays were 30.36 ± 54.04, 43.78 ± 46.7 min, 5.9 ± 4.01 h, were 30.36 ± 54.0, 43.78 ± 46.7 min, 5.9 ± 4.01 and 10.3 ± 4.83 h, respectively. Conclusions RV dysfunction plays the important role in longer recovery and intraoperative time, while its effect is mostly transient. The use of TAPSE and FAC methods is valuable in the evaluation of postoperative outcomes, and the former proved to be more effective.


| INTRODUCTION
Cardiopulmonary bypass (CPB) is a surgical procedure that is commonly used in clinical practice, particularly for the treatment of congenital heart diseases (CHDs) in the pediatric group of patients.
One of the most serious complications associated with it is right ventricle (RV) dysfunction that can lead to profound ischemia and myocardial infarction. 1 CPB guarantees a motionless and bloodless surgical field by involving an extracorporeal circuit to provide physiological support.
Typically, blood is drained by gravity out of the heart and lungs to a reservoir by venous cannulation and tubing. Later, a pump and artificial lung (oxygenator or gas exchanger) facilitate the return of the oxygenated blood to the arterial system. RV dysfunction pathology includes high RV preload or afterload, impaired right coronary artery perfusion, and decreased contractility.
In contrast to the left coronary artery, perfusion of the right coronary artery occurs during the whole heart cycle. Moreover, high RV pressure due to pathological causes such as pulmonary hypertension leads to lower coronary artery perfusion, highlighting the importance of preserving the normal pressure inside the two ventricles.
Additionally, the RV normally provides low-pressure perfusion for the pulmonary vasculature, making it highly sensitive to even moderate increases in pulmonary arterial pressure. However, RV dysfunction is usually a result of different mechanisms, and that is why RV failure is associated with many underlining conditions. Contractility impairment as one of the major causes of RV dysfunction is mainly caused by perioperative RV ischemia and infarction. Volume overload, on the other hand, is commonly developed as a result of tricuspid or pulmonic regurgitation leads.
However, the causes of pressure overload include left-sided valvular disease, cardiomyopathy, pulmonary hypertension, embolism, acute respiratory distress syndrome (ARDS), and high positive-pressure ventilation. Pulmonary hypertension or contractile impairment may lead to RV failure associated with rapid progression to RV dilation, resulting in higher end-diastolic pressure. That can push the ventricular septum toward the already underfilled left ventricle (LV) chamber, which, in its turn, reduces LV preload and decreases CO.
The physiopathological process of RV failure after cardiac surgery is more complex than what we have described above in the traditional model. More than one mechanism is involved in the process, including pulmonary hypertension primarily associated with CPB, pre-existing pulmonary hypertension, and ventricular interdependency. Inflammatory mediators after CPB may mediate the increase in pulmonary resistance and vasoconstriction after CPB.
These mediators may result from endothelial damage or ischemic and reperfusion mechanisms due to inadequate blood flow through the bronchial arteries. As a result, nitric oxide and prostacyclin go down, while thromboxane A2 and endothelin level up. This represents the imbalance between vasoconstriction and vasodilation factors. Additional factors disturb the hemodynamic status of RV and increase pulmonary hypertension, such as administration of heparin and/or protamine, pulmonary microembolism phenomena, ischemia of the RV, metabolic acidosis, hypercapnia, hypothermia, hydric overload, poor myocardial protection, extended extracorporeal circulation time, obstruction of vascular grafts, and loss of auricular-ventricular synchrony.
The relevant diagnostic methods are used to prevent these complications, and one of them is echocardiography.
The echocardiographic machine uses ultrasound waves, and it must have some features to perform standard pediatric echocardiograms. These features must include two-dimensional (2D) imaging, M-mode, pulsed-wave and continuous-wave Doppler, color flow Doppler mapping, electrocardiogram 2D gating, Doppler velocities, and a color monitor. Additionally, it must have the ability to measure cardiac structures and store moving images. A hard-copy paper printout is desirable but not required.
Although evaluating ventricular function is an essential part of every echocardiographic study on children with congenital or acquired heart disease, it is still challenging to evaluate the systolic function. That is because of the confounding effect of different factors, such as ventricular structure and the difference in loading conditions.
Evaluating contractility, on the other hand, is also difficult because of the complex structure physiology of RV. Many indices have been described as surrogate parameters of RV global systolic function. According to the latest guidelines for cardiac chamber quantification, sonographers recommended observing the right heart from various perspectives using multiple acoustic windows.
Additionally, including multiple parameters is strongly needed to give the best result.
During cardiac anesthesia and in the intensive care unit (ICU), clinicians use echocardiography to make the right decisions regarding surgical procedures and perioperative management. 2 Echocardiography, conversely, helps in assessing the hemodynamic status besides static and dynamic parameters such as low CO syndrome, ejection fraction, heart volumes, systolic and diastolic function, valve pathology, pulmonary circulation, ventricular filling pressures, pericardial effusion, and fluid responsiveness. 2,3 Thus, considering the prevalence of heart diseases in children, the use of echocardiography to assess RV performance during the heart cycle is crucial to determine the long-term outcomes of surgery and to take the appropriate intervention in case of poor RV performance, especially if there are congenital diseases present. Therefore, RV evaluation using the appropriate measurements should be performed routinely using various parameters according to the main diagnosis.
In modern clinical practice, the evaluation of RV systolic function is routinely implemented via Doppler tissue imaging, tricuspid annular plane systolic excursion (TAPSE), derived tricuspid lateral annular systolic velocity (S wave), and fractional area change (FAC).

| FAC
The FAC is a 2D measure of RV global systolic function where the normal value is >35% in adults. 4 Using the apical four-chamber view, it is calculated by subtracting the end-diastolic from the end-systolic area and then dividing the result by the end-diastolic area. 5 The image must be optimized under two essential conditions: maximizing the RV area and defining the border of the endocardium in the setting of trabeculations, especially the free wall, to accurately capture the RV cavity. 6 According to the previous studies, FAC correlates with magnetic resonance imaging (MRI)-derived RV ejection fraction (RVEF). Additionally, it can predict the outcomes in adult patients with myocardial infarction and pulmonary hypertension. 7 Figure 1).

| TAPSE
TAPSE is another 2D measuring procedure that evaluates systolic RV function in the M-mode apical four-chamber view by placing the cursor on the lateral section of the tricuspid valve annulus. It assesses the tricuspid valve's excursion by calculating the difference in distance between the annulus and the apex at the end-diastole and end-systole phases. This distance can also be easily quantified with 2D imaging techniques, 13,14 with equally repeatable findings.
Conversely, the load and angle dependence besides the potential influence of the LV's functional status represent big limitations for the procedure. Furthermore, TAPSE does not consider the involvement of the ventricular septum and/or the RV outflow tract in the performance of RV. 15 Considering the pathological change in the contractile pattern of the RV, this measure poorly correlates with MRI-measured EF. Therefore, it should be cautiously used in pediatric patients with RV volume load and single ventricle and is preferably reserved for longitudinal follow-up. 14 As RV function plays a crucial role in the outcomes of patients who undergo cardiac surgery, our study aims to compare the efficacy of TAPSE and FAC in the postoperative measurement of RV function.
This also includes an investigation of the influence of the surgical approach and its correlation with CPB.

| MATERIALS AND METHODS
This is a prospective observational study on pediatric patients with CHD who underwent cardiac surgery at Bhanubhai and Madhuben Patel Cardiac Centre, Shree Krishna Hospital, Karamsad, Anand, Gujarat, India, between January 2019 and January 2020.
A total of 50 patients were enrolled, and the following inclusion criteria were applied: age between 1 month and 18 years and the presence of CHD. Exclusion criteria comprised consisted of preoperative moderate-to-severe RV dysfunction, single ventricle physiology, an abnormal left coronary artery from the PA (ALCAPA), and LV dysfunction besides moderate-to-severe RV dysfunction (Table 3).

| Data collection
The study was approved by the institutional ethics committee, and all the participants provided written informed consent. All the operations, including the aorta-bicaval cannulation, were performed under traditional CPB through median sternotomy. All the surgical procedures were provided access through the right atrium where we crossclamped the aorta, all patients were cooled to 28°C, and cold-blood cardioplegia (CP) was supplied through the aortic root to stop the heart.

| Surgical procedure
Anesthesia was induced and maintained by the weight-related doses of thiopental, fentanyl, midazolam, and pancuronium.
After shifting patients to the operation theater, standard monitoring viz. ECG, pulse oximetry, and invasive blood pressure monitoring, temperature monitoring with the nasopharyngeal probe was done for all the patients enrolled in the study.
The change of fractional area was calculated by delineating the RV endocardial border at the end-diastole and end-systole phases. The difference between the two areas was divided by the area at end-diastole. However, this measure is a reproducible one that is unaffected by pericardiotomy. The normal change for adults is greater than 35%. In this example, it reduced to (26%), which refers to an RV dysfunction. RV, right ventricle/right ventricular.

| Postoperative sedatives
In the postoperative period, analgesia and sedation were achieved via dexmedetomidine infusion at a rate of 0.

| RESULTS
The demographic data and male:female ratios are represented in Table 4 and Figure 3, respectively. The relevant results concerning the comparison of RV and main pulmonary artery (MPA) pressure preoperatively and postoperatively are outlined in Table 5 and  (Figures 6-8). Similarly, the mean values for TAPSE and FAC were obtained in presurgical and postsurgical phases (

| DISCUSSION
The primary goal of this study was to use recognized deformational

| Incidence of RV dysfunction
In the early postoperative period, RV dysfunction is described by elements of prohibitive physiology on Doppler echocardiography (presence of an antegrade diastolic pulmonary flow coinciding with atrial systole). 21,22 According to the literature, its popularity ranges from 28% to 63%. 23 F I G U R E 6 ACC and CPB time correlation. ACC, aortic cross-clamp; CPB, cardiopulmonary bypass.

F I G U R E 7 Correlation of ventilation time and mediastinal drainage in hours
Multiple processes such as increased RV afterload due to pulmonary hypertension affect RV contractility in cases of idiopathic dilated cardiomyopathy (DCM). RV is also affected by cardiomyopathic activity such as ventricular interdependence caused by septal dysfunction and myocardial ischemia due to lessened coronary perfusion. However, RV systolic dysfunction is believed to be a conventional final pathway in heart failure, which may lead to a poor prognosis. [27][28][29] Tricuspid regurgitation forth and indications of foundational venous blockage, like raised jugular venous tensions, foresee higher mortality in patients with cardiovascular breakdown. 30 Excessive right atrial pressure is linked to hepatic and renal dysfunction, leading to malnutrition and cardiorenal syndrome. 31 Because of the related bleakness and mortality as well as abrupt cardiovascular passing in patients with left-sided cardiovascular breakdown, risk stratification in DCM is significant. 32 Due to the related bleakness and mortality as well as abrupt cardiovascular passing in patients with a left-sided cardiovascular breakdown of the significance of RV systolic dysfunction on both morbidity and mortality. 33 CMRI is recommended as the gold standard approach for RV evaluation in guidelines; however, it is not readily available, which is seen as a serious limitation to its use. 34 Nonetheless, echocardiography is a noninvasive, inexpensive, and widely available way of assessing RV performance. Consequently, transthoracic echocardiography is the most common imaging tool for RV evaluation. Despite this, precise RV shape and capacity measurements are challenging because of the RV's complicated structure.
Thus, in this study, we reviewed the echocardiographic modifications of RV aspects and capacity related to persistent cardiovascular breakdown and to foresee the predominance of RV systolic dysfunction in patients with constant cardiovascular breakdown, given echocardiographic boundaries.
Singh et al. 35  In heart failure, Kjaegaard et al. 37